Misfit Dislocations at the Al/αAl2O3 Interface"        Ghanshyam Pilania"

Richard G. Hoagland, Steve M. Valone & Ben Liu!Los Alamos National Laboratory !

Materials Science and Technology Division (MST-8)!Collaborators"

Barend J. Thijsse & Ivan Lazic, Delft University of Technology, Netherlands!

UNCLASSIFIED LA-UR-2014-xxxx

Symposium WW: Defects and Radiation Effects in Advanced Materials"Thursday 2pm, December 4, 2014"Sheraton, 3rd Floor, Fairfax A/B"

2014 MRS Fall Meeting & Exhibit, Boston, MA"

Acknowledgements"John P. Hirth, Scientific Advisory Committee, CMIME,  LANL!

Metal-Ceramic Interfaces"

[1] Chatain et al. Rev. Phys. Appl. 23, 1055 (1988)."[2] Zhang et al. Phys. Rev. B 69, 045423 (2004)."

Knowledge of the metal/ceramic interface structure is necessary for both the fundamental viewpoints and practical applications.1-2"

Metal-Ceramic Joints" Coating Technology" Corrosion Resistance" Microelectronics"Reinforced metals "

Alumina"

Bulk α-Al2O3"

R3cAluminum"Fm3m

Al-Al2O3 interface is one of the most important metal ceramic interface"

Mo+va+on  to  study  Al-­‐Al2O3  interface  structure  

Ø  Experimentally  it  quite  challenging  to  measure  atom-­‐resolved  interface  structure  

Ø  Density  func+onal  theory  based  computa+ons  are  imprac+cal  for  such  “large”  systems  

Ø  Atomis+c  poten+als  of  efficient  molecular  dynamic  simula+ons  are  scarce  

Ø  It  is  a  challenge  to  describe  both  ionic/covalent  and  metallic  bonding  situa+ons  consistently  

Ø  Charge  transfer  effects  at  the  interface  have  to  be  adequately  described  

Why  Al-­‐Al2O3  interface  structure  is  so  poorly  Understood?  

Ø  A  very  limited  amount  of  informa+on  is  available  for  the  Al/Al2O3  interface  

Ø  State-­‐of-­‐the-­‐art  knowledge  is  not  sufficient  for  predic+on  of  mechanical  proper+es  of  Al/Al2O3  mul+layered  heterostructures  

There  is  a  gap  in  our  knowledge  

?  

Details of the Interatomic Potential "

I. Lazic and B. J. Thijsse, Comp. Mat. Sci. 53, 483-492 (2012)."X.W. Zhou, H.N.G. Wadley, J.S. Filhol, M.N. Neurock, Phys. Rev. B 69, 035402 (2004)."

Charge  transferable  interatomic  potenAals    (from  Barend  J.  Thijsse’s  group  at  DelI  University  of  Technology)  

F.H. Streitz, J.W. Mintmire, Phys. Rev. B 50 11996 (1994)."

U =Unes +Ues

Unes =i=1

N

∑ 12j=1

j≠i

N

∑ Sijhij (rij )φij (rij )+ Fii=1

N

∑ (ρi )

Ues = (χ ii=1

N

∑ qi + Jiqi2 )+

qiqjrijj>i

N

∑i=1

N

∑ Pot

entia

l Ene

rgy

per a

tom

(eV

)

Pot

entia

l Ene

rgy

per a

tom

(eV

)

Medlin et al. Thin Solid Films 299 110 (1997)."

Al  

Liquid Metal!

Al2O3  

S. H. Oh et al. Science 330, 489 (2010)."

Al2O3  Al  

Alpas et al. J. Mat. Sci. 25, 1603-1609 (1990)."

Multi-Layers!Interfaces!

Motivation to study Al-Al2O3 interface structure"

Solid-Solid Interface! Solid-Liquid Interface! Heterostructure!

Ø  Misfit dislocation network structure at the Al/αAl2O3 interface has not been quantified!

Ø  Knowledge of the dislocation network is required for prediction of mechanical properties of Al/Al2O3 multilayered heterostructures!

(0001)Al2O3 || (111)Al

[1010]Al2O3 || [110]Al

~ 4% in-plane lattice mismatch"

Orienta+on  Rela+onship  at  Al/α-­‐Al2O3  Interface  

(0001)Al2O3 || (111)Al

[1010]Al2O3 || [110]Al

~4%  in-­‐plane  laRce  mismatch  Medlin et al. Thin Solid Films 299 110 (1997)!

Primary orientation !Relationship  

•  Film  was  grown  at  200°C    

Al-terminated  

O-terminated  (0001)Al2O3

Surface  termina+ons  at  Al(111)/α-­‐Al2O3(0001)  Interface  

S. H. Oh et al. Science 330, 489 (2010).!

Al!

J. Kang et al. Phys. Rev. Lett. 108, 226105 (2012).!

Al!O!

[0110]Al2O3

[101]Al

Relaxed"

Coherent Al/α-Al2O3 Interfaces Relaxed Geometry of the O-terminated Interface!

•  Interface geometries computed using DFT and the potential are in good agreement.!

•  Al metal atoms at the interface occupy the lattice sites which are given by a natural continuation of the α-Al2O3 lattice.!

⊗

⊗

(111)Al ||

(0001)Al2O3

[121]Al

[2110]Al2O3[0110]Al2O3

[101]Al

Al!

Al!

O!

Unrelaxed"[121]Al

[2110]Al2O3

X.-G. Wang et al. Phys. Rev. Lett. 89, 286102 (2002)."

Al!

O!Al!

[101]Al

[0110]Al2O3

Al!

Al!

O!

O-terminated Interface![0110]Al2O3

[101]Al

⊗

⊗

(111)Al ||

(0001)Al2O3

[121]Al

[2110]Al2O3

Coherent Al/α-Al2O3 Interfaces Relative stability: O-terminated v/s Al-terminated Interface!

•  The Al-terminated interface is more stable by: 1.98 J/m2!•  Results from DFT calculations are also in qualitative agreement.!

Al-terminated Interface!

Bulk Al Reservoir !(O-poor condition)!

S. H. Oh et al. Science 330, 489 (2010)."

2D Interface Misfit Dislocation Network "

X 23!

X 24!

4.960 Å!

4.762 Å!

X 23!

3  X 8!

8.248 Å!

2.864 Å!

[2110]Al2O3 [0110]Al2O3

2 8.248×8− 2.86378×238.248×8+ 2.86378×23#

$%

&

'(=1.78×10−3

Misfit Strain"

[2110]Al2O3

Along  

Along  

[0110]Al2O3

2 4.762×24− 4.9602×234.762×24+ 4.9602×23#

$%

&

'(=1.78×10−3

Disregistry vectors with respect to CDP !

= 2.48 Å!be∑

= 57.1 Å!s

Position Along (Å)!

Dis

regi

stry

Com

pone

nt (Å

)!

[2110]Al2O3Hirth et al. Prog. in Mater. Sci. 58 749 (2013)."

0.0 e  

0.9 e  

(111)Al || (0001)Al2O3 [1210]Al2O3 || [112]Al

Layer C  

Layer B  Layer A  

Al  O  

2D Misfit Dislocation Network "

12[110] 1

2[101]

12[011]

16[112]

16[211]

16[121]

0.0 e  

0.9 e  

(111)Al || (0001)Al2O3 [1210]Al2O3 || [112]Al57.1 Å!

Layer C  

Layer B  Layer A  

Al  O  

2D Misfit Dislocation Network "

Charge DistributionCorrelation with the Interface Dislocation Structure!

Layer  B  

0.018 e  

0.021 e  

Layer  A  

0.12 e  

0.15 e  

Layer  C  

0.005 e  

0.010 e  

12[110] 1

2[101]

12[011]

16[112]

16[211]

16[121]

0.0 e  

0.9 e  

(111)Al || (0001)Al2O3 [1210]Al2O3 || [112]Al57.1 Å!

Layer C  

Layer B  Layer A  

Al  O  

2D Misfit Dislocation Network "

Misfit Dislocation Network "After Annealing at 500 K!

HCP!

Node!

FCC!

12[101]

12[110]

16[112]

16[121]

12[011]

16[211]

0.0 e  

0.9 e  

(111)Al || (0001)Al2O3[1210]Al2O3 || [112]Al

HCP!

FCC!

Shao et al. Sci. Rep. 3, 2448 (2013)."Cu(111)/Ni(111)!

HCP!

HCP!

FCC!

FCC!

0.0 e  

0.9 e  

[1210]Al2O3 || [112]Al (111)Al || (0001)Al2O3

Misfit Dislocation Network "After Annealing at 500 K!

Low Stacking Fault Energy!High Stacking Fault Energy!

Influence of Stacking fault Energy"

Dmitriev et al. Comp. Mat. Sci. 29, 95 (2004).!

FCC!HCP!

FCC!

Influence of Dislocation Interaction!

FCC!FCC!

After Annealing  Before Annealing  

Attractive!Interaction  

Repulsive!Interaction  

Summary"•  Coherent and Semi-coherent Al(111)/α-Al2O3(0001)

interfaces have been studied using a charge transferable potential for the first time.!

•  The predicted interface misfit dislocation structure shows a pattern of coherent and stacking fault regions with three sets of edge dislocations.!

•  The interface structure can be understood in terms of a competition between stacking fault energy and dislocation interaction energy.!

•  The results will serve as a crucial input for dislocation dynamics models to simulate mechanical behavior of Al/α-Al2O3 interface and multilayered heterostructures.!

!Future directions:""•  Dislocation dynamics studies to predict mechanical behavior of Al(111)/α-Al2O3(0001)

multilayer heterostructures.!•  Explore other orientational relationships: with (110) Al and stepped Al surface planes.!